Today, the big groups which will certainly be there today are :
VAG (Audi VW, etc.)
PSA (Peugeot-Citroën)
GM (Holden, Cadillac, etc.)
Ford (and brands)
Mercedes (DaimlerChrysler)
Toyota
Renault (+ Nissan)
Fiat Auto spa (Alfa, Lancia, Maserati, etc.) which I hope will remain independant
BMW, Porsche and Rover will probably make links with other car makers, we'll see.
.... and Lada